A transmission display element displays an image, a character, etc., by varying its transmittance in response to a driving signal and modulating the intensity of light emitted from a light source, and the transmission display element itself does not emit light.
Examples of such transmission display element include: a liquid crystal display panel, an electrochromic display, a display using a transmission ceramic such as PLZT (Lead Zirco-Titanate doped with lanthanum), etc. Among the above-listed transmission display elements, the liquid crystal display panel has been used in a variety of fields such as a pocketable TV, a word processor, etc.
A pixel is a minimum display unit, and plural pixels are regularly arranged in the liquid crystal display panel. By applying independent driving voltage to the respective pixels, the optical characteristics of the liquid crystal vary, thereby displaying an image, a character, etc.
Examples of the method of applying an independent driving voltage to each pixel include: a simple matrix method and an active matrix method. In the active matrix method, a driving element such as a thin film transistor (TFT), a metal insulator metal (MIM), etc., is formed on each pixel in order to display an image of improved quality and super resolution.
FIGS. 4(a) and (b) are explanatory views of the present invention. As shown in these figures, the driving element composed of the thin film transistor is arranged such that a semiconductor layer, an insulating layer and electrodes of various types are laminated on a glass substrate 16. More specifically, the semiconductor layer is composed of an amorphous silicon 41 and an anodic oxide film 42, the insulating layer is a gate insulating film 43, and the electrodes are a gate electrode 44, a source electrode 45, a drain electrode 46 and a pixel electrode 17 (liquid crystal driving use electrode) in the example shown in FIGS. 4(a) and (b). FIGS. 5(a) and (b) show an example of a driving element composed of the MIM which comprises the glass substrate 16 whereon an X-electrode (tantalum) 51, an insulating layer, a metal thin film and a pixel electrode 17 (liquid crystal driving use electrode) are laminated. More specifically, the insulating layer is an oxide tantalum 52, and the metal thin film is a chrome thin film 53 in the example shown in FIGS. 5(a) and (b). The X-electrode 51 is connected to the pixel electrode 17 through the-oxide tantalum 52 and the chrome thin film 53.
As described, both the driving element composed of the thin film transistor and the driving element composed of the MIM have a multilayer structure. In order to form the described multilayer structure, a process of patterning each layer on the glass substrate is repetitively performed. In this patterning process, for example, a defective TFT which does not show normal TFT characteristics may generate, and this causes the problem that a voltage cannot be applied to the corresponding pixel electrode 17. The defective pixel to which a voltage cannot be applied always allows light to transmit therethrough, and in the state where the normal pixels surrounding the defective pixel block the transmission of light, the pixel electrode corresponding to the defective TFT would be recognized as a bright defect.
An example of the method of concealing such bright defect is disclosed in Japanese Laid-Open Patent Application No. 2160/1993 (Tokukaihei 5-2160), wherein in a liquid crystal panel 70, light-blocking means 73 made of, for example, a black ultraviolet curing resin is formed on a glass substrate 72 on a light incident side at a position corresponding to a defective luminance point pixel 71 as shown in FIG. 9.
Another example of the method of concealing such bright defect is disclosed in Japanese Laid-Open Patent Application No. 301615/1992 (Tokukaihei 4-301615), wherein in a liquid crystal panel 80, a convex portion 84 is formed on a glass substrate 82 on a light incident side corresponding to a defective luminance point pixel 81, the convex portion 84 being surface-roughened by an excimer laser beam 83 so as to scatter a light beam shed thereon as shown in FIG. 10. By forming this convex portion 84, the light emitted from the light source to be incident on the defective pixel 81 would be scattered, and the amount of light incident on the defective pixel 81 would be reduced to such a level that the luminance point of the defective pixel 81 becomes inconspicuous.
However, in the described conventional methods of concealing the bright defect in the transmission display device, all the light would be blocked or scattered irrespectively of the wavelength of the light. Therefore, when adapting the described method to such transmission color display devices in which three picture elements correspond to a single microlens (see FIGS. 11(a) and (b) which are cross-sectional views in the horizontal direction in the case where the microlens is placed as shown in FIG. 6), the following problems would arise.
In the transmission color display devices shown in FIGS. 11(a) and (b), single-microlens 74 and 85 are provided respectively for plural pixels 71 and 75, and pixels 81 and 86, which correspond to light of plural wavelength bands, i.e., red R, green G and blue B. When applying any one of the above-mentioned two methods to the case where pixels 71 and 81 are defective pixels in these transmission color display devices, not only a beam incident on the defective luminance point pixels 71 and 81, but all the beams incident on all the pixels 71 and 75, 81 and 86 including normal pixels 75 and 86 would be blocked or scattered. Since this causes the amount of light incident on the normal pixels 75 and 86 to be reduced, the normal display would not be performed.